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For the purpose to understand the physical mechanism of
noise which isimportant in photodiodes and photodetectors we
setup a noise measurementmeasurement system to measure the noise
performance of various devices andmaterials. The most
important noise sources in semiconductor devices are
thermalnoise, shot noise, generation-recombination noise and
contact noise. Weanalyze the physical mechanism of the diffusion
and generation-recombinationcurrent which both contribute to the
noise in a diode and derive a universalformula of diode noise
which can be written as 2qIA(V) where A(V) is the noise current
gain. As long as we have the I-V characteristcs of a diode,
according to this formula, we can calculate the theoretical
noise currentgain and noise power and we don''t have to know the
fraction of different current components in the diode. We
design a low noise current preamplifier as the input stage of
the noise measurement system and reduce the background current
noise powerwhich improves the system performance. Then we
measure the noise performanceof two commercial p-n diodes. The
experimental data including noise powerand noise current gain
all agree well with the theoretical value which proves the
correctness of the theory.
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